The present invention relates to a micro-transformer that may provide galvanic isolation between a primary winding and a secondary winding while providing a large step-up or step-down ratio via tight magnetic coupling. The micro-transformer may be implemented in an integrated circuit.
Transformers enable magnetic signal transfer between two or more circuit networks via mutual inductance, while providing direct electrical (i.e., galvanic) isolation. Such isolation may prevent extraneous transient signals, including common-mode transients, from being inadvertently processed as intended signals. Isolation may also protect equipment from shock hazards, or permit equipment on either side of an isolation barrier to operate at different supply voltages without necessarily sharing a common ground connection. Optical isolators are used to provide such isolation by converting input electrical signals to light signals, and then converting the light signals back into electrical signals again, but they have numerous known disadvantages.
Transformers also enable alternating voltages and currents of the magnetically coupled circuit networks to be stepped up or down significantly, ideally with no overall power loss. The ratio of the number of turns in the primary winding to the number of turns in the secondary winding determines the stepping ratio for ideal transformers. Transformers are accordingly used in power supplies and power converters for a wide variety of applications.
Small transformers are often manufactured from discrete components, versus components that can be made by planar processes like those used to manufacture integrated circuits. As used herein, a “micro-transformer” refers to a small transformer in which at least one winding is formed using planar fabrication methods, including but not limited to semiconductor fabrication techniques. At present, micro-transformers are quite limited in stepping ratio and power transfer efficiency.
Accordingly, the inventor has identified a need in the art for an improved micro-transformer to provide the benefits of isolation but with improved stepping ratio and power transfer efficiency.